Creates the union of two rectangles
_WinAPI_UnionRect ( $tRECT1, $tRECT2 )
|$tRECT1||$tagRECT structure that contains the first source rectangle.|
|$tRECT2||$tagRECT structure that contains the second source rectangle.|
|Success:||$tagRECT structure that contains the union of the $tRECT1 and $tRECT2 rectangles.|
|Failure:||Sets the @error flag to non-zero.|
The union is the smallest rectangle that contains both source rectangles. The system ignores the
dimensions of an empty rectangle that is, a rectangle in which all coordinates are set to zero, so that
it has no height or no width.
Search UnionRect in MSDN Library.